IEC 61131-7-2000 PDF

Full title and description

IEC 61131-7:2000 — "Programmable controllers — Part 7: Fuzzy control programming". Defines the Fuzzy Control Language (FCL) and the conventions for specifying fuzzy-control elements and blocks intended for use with programmable controllers (PLCs). The part documents syntax, semantics and integration rules so fuzzy control components can be described, exchanged and embedded within IEC 61131–based control systems.

Abstract

This part of IEC 61131 standardizes a domain‑specific language for fuzzy control (FCL). It specifies constructs for defining linguistic variables, membership functions, fuzzification (FUZZIFY), rule blocks (RULEBLOCK), and defuzzification (DEFUZZIFY), together with aggregation and accumulation methods. The standard enables the representation, exchange and integration of fuzzy control logic in PLC program blocks and provides normative examples and annexes to support implementation.

General information

• Status: Published International Standard (active, stability information available).
• Publication date: 10 August 2000 (IEC publication date).
• Publisher: International Electrotechnical Commission (IEC).
• ICS / categories: 35.240.50, 25.040.40 (automatic controllers; industrial automation).
• Edition / version: Edition 1.0 (2000).
• Number of pages: 113 pages (IEC webstore bibliographic listing).

Scope

Specifies the syntax and semantics of a Fuzzy Control Language for use with programmable controllers, including definitions of fuzzy variables, membership functions, fuzzification/defuzzification operators, rule formats, rule weighting and accumulation strategies. It also defines how fuzzy elements are packaged for use inside IEC 61131 function blocks and provides normative annexes with examples, symbols and abbreviations to aid interoperability. The primary audience is implementers of PLC firmware, tool vendors and system integrators who need a standardized format for fuzzy control logic.

Key topics and requirements

• Definition of the Fuzzy Control Language (FCL) constructs: FUZZIFY, DEFUZZIFY, TERM, RULEBLOCK and RULE entries.
• Specification of membership‑function formats and parameters (triangular, trapezoidal and other common shapes).
• Defined accumulation (ACCU) and aggregation (AND/OR) operators and standard defuzzification methods (for example centre of gravity variants as used in examples).
• Rules syntax including support for rule weights and default actions/values.
• Guidelines for embedding/exchanging FCL descriptions within IEC 61131 function blocks and projects to promote interoperability between tools and PLCs.

Typical use and users

Used by industrial control engineers, PLC and tool manufacturers, system integrators and researchers implementing fuzzy controllers within automation projects. Typical applications include process control, water management, HVAC, and other domains where fuzzy logic provides smoother or more human‑centric control than binary logic. FCL is used to describe fuzzy control elements that are then implemented in PLC function blocks or exchanged between engineering tools.

Related standards

IEC 61131-7 is part of the IEC 61131 family for programmable controllers and complements other parts such as IEC 61131-1 (general information), IEC 61131-3 (programming languages) and IEC 61131-5 (communications). National and regional adoptions (for example as EN/UNE versions) align the part with local standards practice. Implementers typically consult IEC 61131-3 for integration of function blocks and programming models.

Keywords

Fuzzy Control Language (FCL); fuzzy logic; programmable controller; PLC; FUZZIFY; DEFUZZIFY; RULEBLOCK; membership function; defuzzification; IEC 61131.

FAQ

Q: What is this standard?

A: IEC 61131-7:2000 is the part of the IEC 61131 series that standardizes a Fuzzy Control Language (FCL) for representing fuzzy control logic intended for programmable controllers.

Q: What does it cover?

A: It covers syntax and semantics for fuzzy‑control constructs (linguistic variables, terms/membership functions, rule blocks, accumulation and defuzzification methods), examples and guidance for embedding these constructs in IEC 61131 function blocks to enable tool and device interoperability.

Q: Who typically uses it?

A: PLC vendors, control engineers, systems integrators and software/tool vendors that implement or exchange fuzzy control components for industrial automation projects. Researchers working with fuzzy control in industrial contexts also reference it.

Q: Is it current or superseded?

A: IEC 61131-7 was published in 2000 (Edition 1.0). IEC's bibliographic entry lists a stability date indicating the standard remains the reference publication (stability information shown on IEC webstore); users should verify the IEC webstore for any technical corrigenda or later amendments.

Q: Is it part of a series?

A: Yes — it is Part 7 of the IEC 61131 family of standards for programmable controllers; other parts cover general information, equipment tests, programming languages, communications and functional safety.

Q: What are the key keywords?

A: FCL, fuzzy logic, PLC, FUZZIFY, DEFUZZIFY, RULEBLOCK, membership function, defuzzification, programmable controllers.